Management and herd performance of dairy herds with and without chronic wasting disease.

'Chronic wasting' in cattle acquired a special meaning in the Netherlands in 1999. It was used to define animal health problems that were thought to be associated with the use of bovine herpesvirus 1 marker vaccine. Criteria have not been set by which an objectively independent inventory of the problems could be made. The objective of this study was to determine management factors associated with the problem of 'chronic wasting' prior to the use of the BHV1 marker vaccine. Knowledge about these factors could be helpful for generating additional hypotheses about the aetiology of chronic wasting in cattle. A total of 188 farms participated in the study, of which 94 had severe problems with chronic wasting. The other half consisted of control farms matched with the case farms that did not report problems after the use of the BHV1 marker vaccine. Data analyses were performed over the period before (and not at the time of) 'chronic wasting' problems. Data were collected from various sources. A questionnaire was used to collect information on farm management practice. In addition, information on laboratory submissions for 1996 to 1998, animal movements in 1998, roughage analyses of 1997 and 1998, expenses for animal health in 1998, and herd performance in 1995 to 1999 was collected. In the analyses, a distinction was made between information obtained objectively and subjectively. Herds with problems of 'chronic wasting' were larger than herds without wasting problems (animals, surface) but not more intensively managed. 'Wasting' herds had a lower performance in terms of fertility and udder health. In addition, these herds had more contact with other herds through the purchase of animals. There were no differences in farm management practices related to disease control and prevention. Additional studies are required with regard to the patho-physiology of chronic wasting cows. The role of herd size needs more study.